in NUE of higher levels population and ecosystem and therefore improving NUE of
individual plants can lead to higher agronomic yield under field conditions.
NUE is dependent on genetics and physiology of crops, environmental factors,
and the mineral nutrient itself. Broadly, NUE depends on the following three factors:
1. Plant/crop type: Innate ability of plant of uptake and assimilate nutrients is
certainly the most important factor influencing the NUE. Internal factors such
as growth form (herb, shrub, tree), physiology (C3 and C4; intracellular and
intercellular pH), time of harvest (annual, biennial perennial) affect the NUE
(Wang et al. 2018). A combination of such internal factors translates into
differing NUE of mineral nutrients among cultivars of various crop species
such as rice, maize, rapeseed, potato (Zhang et al. 2009; Li et al., 2017c; Stahl
et al. 2019; Getahun et al. 2019).
2. Environment: It is the second important factor that directly affects the NUE, and
includes of both below ground (soil) and above ground factors. Biotic factors of
the soil include microbes, mycorrhiza, pests, and weeds, while abiotic factors
include water availability and soil pH (Loqué et al. 2003; Bucher 2007; Hasan
et al. 2016; Wang et al. 2018; Penn and Camberato 2019). Environment of above
ground includes temperature, light and pollution and humidity. All of these are
capable of positively or negatively affecting the NUE directly by altering the
nutrient availability or plant growth. For instance, nitrate uptake is dependent on
water availability (Buljovcic and Engels 2001); and drought stress hampers
P-uptake and P-use efficiency of plants (Garg et al. 2004). Circadian clock has
been shown to regulate phosphate transporter PHT4;1, and influence innate
immunity against Pseudomonas syringae in A. thaliana (Wang et al. 2011).
Pollutants such as SO 2 , H 2 S are known to alter the concentration of the nutrients
(Aghajanzadeh et al. 2016).
3. Nutrient: Physiochemical properties of individual mineral nutrient and regulatory
mechanisms guiding their uptake and assimilation processes in plant are the third
most critical factor influencing NUE. Complex interactions exist among the
regulatory pathways involved in uptake, transport, and assimilation of mineral
nutrients as is evident from the large number of shared transporters (Tables 5.4
and 5.5). Several mineral nutrients also use multiple transporters for uptake and
assimilation (Tables 5.4 and 5.5). Some of the nutrients such as Na and K share
common uptake transporter (HAK5) and uptake mechanism; and application of
NaCl plays negative role in uptake of K (Nieves-Cordones et al. 2010). This has
also been reported both in N and S, where S-deficiency can be overcome by
optimizing N supply in B. napus (Abdallah et al. 2010); as well as P and S where
the sulfate transporters are upregulated under phosphate stress (Rouached 2011).
Another example is the antiporter family which is shared by H+/Ca2+, H+/Cu2+,
and H+/Na+ for uptake and transport. Similarly, ZIP family of transporter is
shared by Cu2+, Fe2+, Fe3+, Mn2+, Ni+, and Zn2+. Members of YSL family are
shared by Cu2+, Mn2+, Ni+, and Zn2+. Phosphate-starvation has also been
shown to reduce concentration of several other mineral nutrients such as Boron,
5 Plant Roots and Mineral Nutrition: An Overview of Molecular Basis of Uptake and. . . 163
individual plants can lead to higher agronomic yield under field conditions.
NUE is dependent on genetics and physiology of crops, environmental factors,
and the mineral nutrient itself. Broadly, NUE depends on the following three factors:
1. Plant/crop type: Innate ability of plant of uptake and assimilate nutrients is
certainly the most important factor influencing the NUE. Internal factors such
as growth form (herb, shrub, tree), physiology (C3 and C4; intracellular and
intercellular pH), time of harvest (annual, biennial perennial) affect the NUE
(Wang et al. 2018). A combination of such internal factors translates into
differing NUE of mineral nutrients among cultivars of various crop species
such as rice, maize, rapeseed, potato (Zhang et al. 2009; Li et al., 2017c; Stahl
et al. 2019; Getahun et al. 2019).
2. Environment: It is the second important factor that directly affects the NUE, and
includes of both below ground (soil) and above ground factors. Biotic factors of
the soil include microbes, mycorrhiza, pests, and weeds, while abiotic factors
include water availability and soil pH (Loqué et al. 2003; Bucher 2007; Hasan
et al. 2016; Wang et al. 2018; Penn and Camberato 2019). Environment of above
ground includes temperature, light and pollution and humidity. All of these are
capable of positively or negatively affecting the NUE directly by altering the
nutrient availability or plant growth. For instance, nitrate uptake is dependent on
water availability (Buljovcic and Engels 2001); and drought stress hampers
P-uptake and P-use efficiency of plants (Garg et al. 2004). Circadian clock has
been shown to regulate phosphate transporter PHT4;1, and influence innate
immunity against Pseudomonas syringae in A. thaliana (Wang et al. 2011).
Pollutants such as SO 2 , H 2 S are known to alter the concentration of the nutrients
(Aghajanzadeh et al. 2016).
3. Nutrient: Physiochemical properties of individual mineral nutrient and regulatory
mechanisms guiding their uptake and assimilation processes in plant are the third
most critical factor influencing NUE. Complex interactions exist among the
regulatory pathways involved in uptake, transport, and assimilation of mineral
nutrients as is evident from the large number of shared transporters (Tables 5.4
and 5.5). Several mineral nutrients also use multiple transporters for uptake and
assimilation (Tables 5.4 and 5.5). Some of the nutrients such as Na and K share
common uptake transporter (HAK5) and uptake mechanism; and application of
NaCl plays negative role in uptake of K (Nieves-Cordones et al. 2010). This has
also been reported both in N and S, where S-deficiency can be overcome by
optimizing N supply in B. napus (Abdallah et al. 2010); as well as P and S where
the sulfate transporters are upregulated under phosphate stress (Rouached 2011).
Another example is the antiporter family which is shared by H+/Ca2+, H+/Cu2+,
and H+/Na+ for uptake and transport. Similarly, ZIP family of transporter is
shared by Cu2+, Fe2+, Fe3+, Mn2+, Ni+, and Zn2+. Members of YSL family are
shared by Cu2+, Mn2+, Ni+, and Zn2+. Phosphate-starvation has also been
shown to reduce concentration of several other mineral nutrients such as Boron,
5 Plant Roots and Mineral Nutrition: An Overview of Molecular Basis of Uptake and. . . 163